PROJECT SUMMARY/ABSTRACT MYC is one of the most important human oncoproteins, contributing to the deaths of an estimated 100,000 Americans each year. The pro-tumorigenic actions of MYC stem from its function as a sequence-specific transcription factor, binding DNA to regulate transcription of thousands of genes connected to ectopic cell growth and proliferation, metastasis, and genome instability. Decades of research into how MYC recognizes its cognate DNA binding sites in the context of chromatin have revealed that, in addition to DNA sequence, there is a strong epigenetic signature for MYC genomic binding sites, marked by methylation of lysine 4 on histone H3 (H3K4me3) and unmethylated CpG dinucleotides. Precisely how these epigenetic marks function to direct MYC to chromatin, however, is unknown. The long term objectives of my work are to understand the molecular mechanisms through which epigenetic determinants contribute to target gene selection by MYC, centering on the recently discovered role of WDR5 as a co-factor for chromatin binding by and tumorigenesis by MYC. WDR5 interacts directly with MYC, co-localizes extensively with MYC across the genome, and is dispensable for DNA-binding by MYC but essential for target gene recognition in the context of chromatin. In association with other proteins, WDR5 has connections to both histone H3K4 methylation and recognition of unmethylated CpG dinucleotides, raising the possibility that WDR5 functions as part of a molecular complex that interprets the epigenetic signature for target gene binding by MYC in vivo. The precise objectives of this work are two-fold. First, to define the molecular context in which MYC and WDR5 associate, using a combination of biochemical and comparative genomic approaches to identify components of the MYC?WDR5 complex and determine their genome-wide interactions on chromatin. Second, to use genome-editing and genome-engineering techniques to manipulate the individual proteins and DNA sequences to directly evaluate their role in the recruitment of MYC and WDR5 to chromatin. Together these Aims will define the mechanism through which epigenetic processes control target gene selection by MYC, and have the potential to reveal new strategies to block MYC function in cancer cells. This research program will also provide an exceptional training experience centered on a cancer-focused research project within the vibrant research environment at Vanderbilt University. The education, training, collaborations, and career development program detailed in this proposal will support my career objective of becoming an independent and impactful cancer researcher.